March 1, 2021 - Snow in Northeastern United States

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   Snow in Northeast US,
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   Several snowstorms swept across the United States in February 2021,
   leaving a lingering layer of snow atop parts of the Appalachian
   Mountains, the Mid-Atlantic, and the Northeast. The Moderate Resolution
   Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite
   acquired a stunning false-color image that highlighted snow and ice on
   February 25.

   Even though a satellite image looks similar to a snapshot taken from a
   phone or camera, it’s not actually the same thing. Satellite
   instruments collect various data through “bands”, with each band
   collecting different data. To make an image, scientists will combine
   data from three bands, assigning each a color: red, blue, or green.
   Because each band collects different data, the resulting image will
   highlight (make visible) different aspects of what is happening on
   Earth.

   A true-color image (bands 1,4,3) appears very much like what we see
   with our own eyes, because these bands actually measure red, green, and
   blue (visible) light. A false-color image uses data from at least one
   non-visible wavelength, but the bands are still represented in red,
   green, or blue. As a result, the final image appears shows the Earth
   differently from how our eyes would see, revealing unique aspects of
   the land, water, or atmosphere that cannot be seen with our own eyes.

   This image uses the combination of Bands 3,6,7 to reveal snow and ice.
   These are highly reflective in visible light (Band 3) and very
   absorbent in short-wave infrared (Bands 6 and 7). When assigned the
   colors of red, green, and blue and combined into an image, snow and ice
   appear bright red—and the thicker the ice or snow, the brighter the red
   shows up. Small amounts of ice crystals, such as in high-level clouds,
   will show up in faint reddish-orange or peach tones. Vegetation
   reflects in Band 6, so will appear green. Bare soil will appear bright
   cyan (greenish blue) while liquid (lakes, streams and oceans) appears
   very dark and cloud show up as white. Using this color combination, it
   is easy to see that snow sits atop the ridges of the Appalachians from
   West Virginia northward and blankets the ground from northern Maryland
   to the states of Vermont and New Hampshire and across southern Quebec,
   Canada. It would be difficult to discern cloud from snow in a
   true-color image, but here it is simple to tell them apart.

   If you want to learn more about how false-color satellite imagery is
   created and utilized, you will want to check out an article published
   by NASA’s Earth Observatory. The article, titled “Why is that Forest
   Red and that Cloud Blue? How to Interpret a False-Color Satellite
   Image” is available  here.

   Image Facts
   Satellite:  Terra
   Date Acquired: 2/25/2021
   Resolutions:  1km (403 KB),  500m (1 MB),  250m (2.2 MB)
   Bands Used: 3,6,7
   Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2021-03-01
 
